CQL for Cassandra 1.2

Subproperties of compaction

Using CQL, you can configure compaction for a table by constructing a map of the compaction
property and the following subproperties:

CQL Compaction Subproperties

Compaction Subproperties

Description

Default

Supported Strategy

bucket_high

Size-tiered compaction strategy (STCS) considers SSTables to be within the same bucket
if the SSTable size diverges by 50% or less from the default bucket_low and default
bucket_high values: [average-size × bucket_low, average-size ×
bucket_high].

1.5

STCS

bucket_low

Same as above.

0.5

STCS

max_threshold

In SizeTieredCompactionStrategy, sets the maximum number of
SSTables to allow in a minor compaction. In LeveledCompactionStrategy, it
applies to L0 when L0 gets behind, that is, when L0 accumulates more than
MAX_COMPACTING_L0 SSTables.

32

STCS

min_threshold

In SizeTieredCompactionStrategy sets the minimum number of SSTables to trigger a minor
compaction.

4

STCS

min_sstable_size

The SizeTieredCompactionStrategy groups SSTables for compaction
into buckets. The bucketing process groups SSTables that differ in size by less than 50%.
This results in a bucketing process that is too fine grained for small SSTables. If your
SSTables are small, use min_sstable_size to define a size threshold (in bytes) below which
all SSTables belong to one unique bucket.

50MB

STCS

sstable_size_in_mb

The target size for SSTables that use the leveled compaction strategy (LCS). Although
SSTable sizes should be less or equal to sstable_size_in_mb, it is possible to have a larger
SSTable during compaction. This occurs when data for a given partition key is exceptionally
large. The data is not split into two SSTables.

160MB

LCS

tombstone_compaction_interval

The minimum time to wait after an SSTable creation time before considering the SSTable
for tombstone compaction. Tombstone compaction is the compaction triggered if the SSTable
has more garbage-collectable tombstones than tombstone_threshold.

1 day

all

tombstone_threshold

A ratio of garbage-collectable tombstones to all contained columns, which if exceeded
by the SSTable triggers compaction (with no other SSTables) for the purpose of purging the
tombstones.